June 2018 Update
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Ingy döt Net
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5278 changed files with 84726 additions and 14379 deletions
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Task/The-ISAAC-Cipher/Modula-2/the-isaac-cipher.mod2
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Task/The-ISAAC-Cipher/Modula-2/the-isaac-cipher.mod2
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MODULE RosettaIsaac;
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FROM Strings IMPORT
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Length, Assign, Append;
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FROM STextIO IMPORT
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WriteString, WriteLn;
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FROM Conversions IMPORT
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CardBaseToStr;
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CONST
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MaxStrLength = 256;
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TYPE
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TMode = (iEncrypt, iDecrypt);
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TString = ARRAY [0 .. MaxStrLength - 1] OF CHAR;
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TCardIndexedFrom0To7 = ARRAY [0 .. 7] OF CARDINAL;
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VAR
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(* TASK globals *)
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Msg: TString = 'a Top Secret secret';
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Key: TString = 'this is my secret key';
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XCTxt: TString = ''; (* XOR ciphertext *)
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MCTxt: TString = ''; (* MOD ciphertext *)
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XPTxt: TString = ''; (* XOR decryption (plaintext) *)
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MPTxt: TString = ''; (* MOD decryption (plaintext) *)
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Mode: TMode = iEncrypt;
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HexTxt: TString;
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(* ISAAC globals *)
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(* external results *)
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RandRsl: ARRAY [0 .. 256] OF CARDINAL;
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RandCnt: CARDINAL;
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(* internal state *)
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MM: ARRAY [0 .. 256] OF CARDINAL;
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AA: CARDINAL = 0;
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BB: CARDINAL = 0;
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CC: CARDINAL = 0;
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PROCEDURE Isaac;
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VAR
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I, X, Y: CARDINAL;
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BEGIN
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CC := CC + 1; (* CC just gets incremented once per 256 results *)
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BB := BB + CC; (* then combined with BB *)
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FOR I := 0 TO 255 DO
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X := MM[I];
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CASE (I MOD 4) OF
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0: AA := AA BXOR (AA SHL 13); |
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1: AA := AA BXOR (AA SHR 6); |
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2: AA := AA BXOR (AA SHL 2); |
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3: AA := AA BXOR (AA SHR 16);
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ELSE
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END;
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AA := MM[(I + 128) MOD 256] + AA;
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Y := MM[(X SHR 2) MOD 256] + AA + BB;
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MM[I] := Y;
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BB := MM[(Y SHR 10) MOD 256] + X;
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RandRsl[I] := BB;
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END; (* FOR *)
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RandCnt := 0; (* Prepare to use the first set of results. *)
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END Isaac;
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PROCEDURE Mix(VAR A: TCardIndexedFrom0To7);
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BEGIN
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A[0] := A[0] BXOR A[1] SHL 11; A[3] := A[3] + A[0]; A[1] := A[1] + A[2];
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A[1] := A[1] BXOR A[2] SHR 2; A[4] := A[4] + A[1]; A[2] := A[2] + A[3];
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A[2] := A[2] BXOR A[3] SHL 8; A[5] := A[5] + A[2]; A[3] := A[3] + A[4];
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A[3] := A[3] BXOR A[4] SHR 16; A[6] := A[6] + A[3]; A[4] := A[4] + A[5];
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A[4] := A[4] BXOR A[5] SHL 10; A[7] := A[7] + A[4]; A[5] := A[5] + A[6];
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A[5] := A[5] BXOR A[6] SHR 4; A[0] := A[0] + A[5]; A[6] := A[6] + A[7];
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A[6] := A[6] BXOR A[7] SHL 8; A[1] := A[1] + A[6]; A[7] := A[7] + A[0];
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A[7] := A[7] BXOR A[0] SHR 9; A[2] := A[2] + A[7]; A[0] := A[0] + A[1];
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END Mix;
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PROCEDURE RandInit(Flag: BOOLEAN);
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VAR
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I, J: CARDINAL;
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A: TCardIndexedFrom0To7;
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BEGIN
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AA := 0; BB := 0; CC := 0;
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A[0] := 2654435769; (* $9e3779b9: the golden ratio *)
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FOR J := 1 TO 7 DO
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A[J] := A[0];
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END;
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FOR I := 0 TO 3 DO (* Scramble it *)
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Mix(A);
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END;
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FOR I := 0 TO 255 BY 8 DO (* Fill in MM[] with messy stuff. *)
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IF Flag THEN (* Use all the information in the seed. *)
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FOR J := 0 TO 7 DO
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A[J] := A[J] + RandRsl[I + J];
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END;
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END;
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Mix(A);
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FOR J := 0 TO 7 DO
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MM[I + J] := A[J];
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END;
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END; (* FOR I*)
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IF Flag THEN
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(* Do a second pass to make all of the Seed affect all of MM *)
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FOR I := 0 TO 255 BY 8 DO
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FOR J := 0 TO 7 DO
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A[J] := A[J] + MM[I + J];
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END;
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Mix(A);
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FOR J := 0 TO 7 DO
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MM[I + J] := A[J];
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END;
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END; (* FOR I *)
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END;
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Isaac(); (* Fill in the first set of results *)
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RandCnt := 0; (* Prepare to use the first set of results *)
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END RandInit;
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(* Seed ISAAC with a given string.
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The string can be any size. The first 256 values will be used. *)
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PROCEDURE SeedIsaac(Seed: ARRAY OF CHAR; Flag: BOOLEAN);
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VAR
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I, M: CARDINAL;
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BEGIN
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FOR I := 0 TO 255 DO
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MM[I] := 0;
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END;
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M := Length(Seed);
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FOR I := 0 TO 255 DO
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(* In case seed has less than 256 elements *)
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IF I > M THEN
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RandRsl[I] := 0
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ELSE
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(* Modula-2 strings are 0-based (at least, in this case). *)
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RandRsl[I] := ORD(Seed[I]);
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END;
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END;
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(* Initialize ISAAC with seed. *)
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RandInit(Flag);
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END SeedIsaac;
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(* Get a random 32-bit value 0..MAXINT *)
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PROCEDURE GetRandom32Bit(): CARDINAL;
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VAR
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Result: CARDINAL;
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BEGIN
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Result := RandRsl[RandCnt];
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INC(RandCnt);
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IF RandCnt > 255 THEN
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Isaac();
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RandCnt := 0;
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END;
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RETURN Result;
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END GetRandom32Bit;
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(* Get a random character in printable ASCII range. *)
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PROCEDURE GetRandomChar(): SHORTCARD;
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BEGIN
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RETURN GetRandom32Bit() MOD 95 + 32;
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END GetRandomChar;
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(* Convert an ASCII string to a hexadecimal string. *)
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PROCEDURE ASCII2Hex(Source: ARRAY OF CHAR; VAR OUT Destination: ARRAY OF CHAR);
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VAR
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I: CARDINAL;
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NumbHex: ARRAY [0 .. 1] OF CHAR;
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BEGIN
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Assign('', Destination);
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FOR I := 0 TO Length(Source) - 1 DO
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CardBaseToStr(ORD(Source[I]), 16, NumbHex);
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IF Length(NumbHex) <= 1 THEN
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Append('0', Destination);
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END;
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Append(NumbHex, Destination);
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END;
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END ASCII2Hex;
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(* XOR encrypt on random stream. *)
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PROCEDURE Vernam(Msg: ARRAY OF CHAR; VAR OUT Destination: ARRAY OF CHAR);
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VAR
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I: CARDINAL;
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OrdMsgI: SHORTCARD;
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BEGIN
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Assign('', Destination);
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FOR I := 0 TO Length(Msg) - 1 DO
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OrdMsgI := ORD(Msg[I]);
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Append(CHR(GetRandomChar() BXOR OrdMsgI), Destination);
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END;
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END Vernam;
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(* Get position of the letter in chosen alphabet *)
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PROCEDURE LetterNum(Letter, Start: CHAR): SHORTCARD;
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BEGIN
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RETURN ORD(Letter) - ORD(Start);
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END LetterNum;
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(* Caesar-shift a character <Shift> places: Generalized Vigenere *)
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PROCEDURE Caesar(M: TMode; Ch: CHAR; Shift, Modulo: INTEGER; Start: CHAR): CHAR;
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VAR
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N, IntOrdStart: INTEGER;
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BEGIN
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IF M = iDecrypt THEN
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Shift := -Shift;
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END;
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N := LetterNum(Ch, Start);
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N := N + Shift;
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N := N MOD Modulo;
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IF N < 0 THEN
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N := N + Modulo;
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END;
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IntOrdStart := ORD(Start);
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RETURN CHR(IntOrdStart + N);
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END Caesar;
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(* Vigenere mod 95 encryption & decryption. *)
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PROCEDURE Vigenere(Msg: ARRAY OF CHAR; M: TMode; VAR OUT Destination: ARRAY OF CHAR);
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VAR
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I: CARDINAL;
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BEGIN
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Assign('', Destination);
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FOR I := 0 TO Length(Msg) - 1 DO
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Append(Caesar(M, Msg[I], GetRandomChar(), 95, ' '), Destination);
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END;
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END Vigenere;
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BEGIN
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(* (1) Seed ISAAC with the key *)
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SeedIsaac(Key, TRUE);
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(* (2) Encryption *)
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Mode := iEncrypt;
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(* (a) XOR (Vernam) *)
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Vernam(Msg, XCTxt);
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(* (b) MOD (Vigenere) *)
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Vigenere(Msg, Mode, MCTxt);
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(* (3) Decryption *)
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Mode := iDecrypt;
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SeedIsaac(Key, TRUE);
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(* (a) XOR (Vernam) *)
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Vernam(XCTxt, XPTxt);
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(* (b) MOD (Vigenere) *)
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Vigenere(MCTxt, Mode, MPTxt);
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(* program output *)
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WriteString('Message: '); WriteString(Msg); WriteLn;
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WriteString('Key : '); WriteString(Key); WriteLn;
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ASCII2Hex(XCTxt, HexTxt);
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WriteString('XOR : '); WriteString(HexTxt); WriteLn;
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ASCII2Hex(MCTxt, HexTxt);
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WriteString('MOD : '); WriteString(HexTxt); WriteLn;
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WriteString('XOR dcr: '); WriteString(XPTxt); WriteLn;
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WriteString('MOD dcr: '); WriteString(MPTxt); WriteLn;
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END RosettaIsaac.
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